Blogs are not supposed to be a place for debate and arguing with the OP but advice and feedback are okay, and often freely given. So, you're good to go. But there are so many threads here and only so much time, that sometimes posts won't be answered right away.
Getting to your situation...
To me it sounds like you and Q are in pretty good shape. You are able to talk about hard topics and difficult feelings, and he seems willing to make adjustments for you to be comfortable. Where I do see potential for some problems to possibly crop up is that you seem like you get impatient with yourself, and judge yourself a bit too much. It's like you seem to say, "I should be more okay with this than I am, what's wrong with me? Well, let me walk into the fire so I can feel the heat and pain and get it over with and handle it better." And then you look around at your partner and his new gf, who are in different places, and you say, "Hey, wait, you aren't with me? WTF? What am I doing wrong?"
If I were you, I would tell Q that you are comfortable right now with him seeing Miss M once a week, and that you want him to read Opening Up
and talk with you about it before it increases to more often than that. Or you can read it together. Tell him you want him to be happy, but need time to absorb and deal with each step along the way. This is the beginning of making agreements.
I strongly feel that no one should make rules about relationships they are not in, but a partner's needs are important and it's often been said that it is a good idea to go at the pace of the one struggling the most. I think you are wise not to forbid them from having sex. And it's perfectly okay that you are also looking out for you in a few ways (asking for a curfew, and wanting something to be special with the, "No hardware on your dick when you're with her"). Know that these boundaries may eventually need to be relaxed after a time, but you are not being unreasonable now. Time constraints and other obligations that make time management an issue are definitely something that needs to be respected by everyone.
No one needs to rush into anything, whether it is Q getting involved with Miss M, you trying to make yourself feel okay with it, or Miss M becoming a friend of yours. They just started seeing each other and having sex, so it can only be a good thing for them to temper it a bit and not get lost in the euphoria that the hormones bring up. It's only brain chemistry - they don't need to give into it just because they want it. See this site: Your Brain on Sex
Keep talking, keep looking at your thoughts and feelings, and be aware of old, self-defeating beliefs. You can also tell him about this site and this thread and have him join, read, and add his side of the story so both of you can get guidance and feedback.